270 CARNEGIE INSTITUTION 



atmospheric content of carbon dioxide and of the concentration of 

 caicium ions in the solution. The solubility of gypsum is a func- 

 tion of the concentrations of calcium ions and sulphate ions. By a 

 comparison of the solubility curves of the two salts as affected by 

 these variable factors, it is possible that a point may be found where 

 the curves intersect in a way which might permit a reversal of the 

 usual order of precipitation. If such a point is found, it would 

 throw light on the condition of the atmosphere and of the surface 

 of the earth at the geological period involved. The necessary cal- 

 culations will be restricted at present to solutions of the ions in 

 question, and may later be made to include the other ordinary con- 

 stituents of sea water. 



Three of the papers, contemplated as preliminary reports on the 

 foregoing studies, are partially prepared and might be speedily com- 

 pleted were not deliberation and a review of the grounds involved 

 in these complex themes more important than early production. 



Chicago, September //, igo^. 



